First: “People joke about it but,” he paused for a long time, “the proof is in the pudding.”

You don’t have to look far to see “proof in the pudding” of climate change in Maine. Last year, the number of Maine shrimp reached a historic low for the 34 years they have been counted, despite the closure of the fishery for four consecutive years. The most widely accepted explanation is not overfishing but climate change. Canada, with its colder waters, still has an active shrimp fishery.

Green algae blooms, spurred by warming waters for the last two summers in Casco Bay, were followed by a rare late-season invasion of toxic Pseudo-nitzschia phytoplankton this winter, affecting hundreds of acres of clam flats and at least 12 mussel and oyster farms. A scientific study published last year links increases in Pseudo-nitzschia with warming waters because of climate change.

Ten years ago, the New York Times reported that with rising temperatures in Quebec, killing spring frosts were happening half as often as in the 1950s. This gave Quebec wild blueberry growers “the confidence to expand production to take advantage of skyrocketing worldwide demand.” Two years ago, Quebec wild blueberry production outpaced Maine’s, and Quebec’s production, along with competition from cultivated berries, has been “a major reason for the glut” in the blueberry market, leading prices to plummet from $1 per pound 10 years ago to as low as 25 cents per pound — half the cost of production.

The “proof in the pudding” of climate change in Maine is lost income, lost jobs and disrupted lives.

The Paris Climate Agreement is the result of an international effort to respond to the impacts of greenhouse gases, beginning as long ago as the 1972 United Nations Conference on the Human Environment. Never before have humans come together to tackle such a grave and complex risk to the planet.

In 1992, 154 nations signed the UN Framework Convention on Climate Change, committing to work toward the “stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.” President George H.W. Bush attended the conference to negotiate that agreement, signed it, and the Senate ratified it.

Maine joined in a lawsuit against the George W. Bush administration, which resulted in a landmark 2007 U.S. Supreme Court decision confirming that the 1970 Clean Air Act not only authorizes the Environmental Protection Agency to regulate greenhouse gases, but requires it to do so, if the gases “may reasonably be anticipated to endanger public health or welfare.” Former President Barack Obama’s EPA found that they did, and that’s one action that Trump’s EPA has not undone.

Recent research indicates that the greenhouse gas carbon dioxide, at the higher levels that most Americans are now routinely exposed to in indoor air, significantly impairs our ability to think. According to researchers at the Harvard School of Public Health, crisis response, information usage, and strategy were most impacted.

The most important thing we can do is to vote, and to often let our politicians know how we feel. Sens. Angus King and Susan Collins and Rep. Chellie Pingree have shown strong leadership on climate, though Collins’ vote for the tax bill allowing oil and gas drilling in the Arctic National Wildlife Refuge is very disturbing. Rep. Bruce Poliquin remains evasive on climate change and did not respond to multiple requests to be interviewed for this column.

Sharon S. Tisher is a lecturer in the School of Economics and the Honors College at the University of Maine. She is a member of the Maine chapter of the Scholars Strategy Network, which brings together scholars across the country to address public challenges and their policy implications. Members’ columns appear in the BDN every other week. Harold W. Borns Jr., is a glacial and Ice Age geologist, professor emeritus of the Climate Change Institute and the School of Earth and Climate Sciences of the University of Maine.